The present invention relates to improvements in a belt-type power transmission, and more particularly, it relates to improvements in cooling for air cooling the belt of a belt-type power transmission.
In motorcycles with relatively small engine output, automatic transmissions of the belt-type are commonly used for transmitting rotation of the engine output shaft to the drive wheel. These automatic transmissions generally include a V belt and variable diameter pulleys. In power transmissions of this type, heat develops by friction between the belt and the pulleys. Particularly, the generation of heat is greater where the distance between the left and right portions of for example, the drive pulley is changed to vary the effective pulley diameter to produce a stepless speed change.
In such automatic transmissions, as is well known, heat which is generated by friction heating of the belt becomes a serious problem because the entire transmission is provided in a casing which includes a transmission case proper and a cover. The cover is provided for preventing dust, muddy water and the like from entering into the transmission. However, the cover tends to trap the heat generated in the belt.
Further, the transmission casing also generally houses auxilliary systems, such as the starter system so that the casing is larger than that which is needed only for incorporating the belt. In conventional transmission mechanisms, the transmission casing constitutes a single compartment.
Commonly, air cooling of the belt and the compartment is performed by installing fins on the drive pulley which is provided on the drive shaft so that it may function as a fan producing air flow in the transmission casing. In the conventional casing comprising a single compartment, air produced by the fins on the fan does not necessarily concentrate on the belt portion where the majority of heat is produced, but rather flows to other portions inside the casing. Moreover, the speed of air flow is not very great through the entire casing.